Laboratoire de Mécanique des Fluides et d'Acoustique - UMR 5509

LMFA - UMR 5509
Laboratoire de Mécanique des Fluides et d’Acoustique
Lyon
France


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Stage de M2 au LMFA

Stage de M2 au LMFA

Helical motion in liquid metals

Encadrants :
Wouter Bos, Alexandre Delache
courriel

Abstract
We propose the investigation of the generation of helical motion in a conducting fluid.

Project

The presence of helicity in a flow is known to be favorable in the process of magnetic field generation, an important example being the generation of the magnetic field of the earth [1]. The understanding of the generation and sustainment of the helicity in geophysical flows is however still partial. One interesting feature is the segregation of helicity, i.e., the fact that helicity of one sign is observed in one part of the mantle of the earth, whereas an opposite
helicity is observed at the other side [2]. This effect will be studied in detail in simplified geometry.

The student will learn to use and modify an inhouse numerical code [3] which allows to study turbulent flows at high Reynolds number. He or she is expected to learn the theoretical back-ground of the project and to assess theoretical predictions on helicity generation in the presence of a strong imposed magnetic field using state of the art numerical simulations of magnetohydrodynamical turbulence.

References
[1] H.K. Moffatt. Magnetic field generation in electrically conducting fluids. Cambridge
University Press, 1978.
[2] P.A. Davidson and A. Ranjan. On the spatial segregation of helicity by inertial waves in dynamo simulations and planetary cores. Journal of Fluid Mechanics, 851:268–287, 2018.
[3] B. Favier, F. S. Godeferd, C. Cambon, and A. Delache. On the two-dimensionalization of quasistatic magnetohydrodynamic turbulence. Phys. Fluids, 22:075104, 2010.